1. Field of the Invention
The present invention relates to a nonvolatile ferroelectric memory.
2. Description of the Prior Art
A ferroelectric memory is a nonvolatile memory and therefore retains the data stored therein even when it is not receiving electric power. A ferroelectric memory requires rewriting of data after reading of data, because a read operation destroys the data stored in a ferroelectric memory. Inconveniently, a conventional ferroelectric memory, when left in a high-temperature environment for a long time after the writing of data, changes its characteristics in such a way that data that is inverted as compared with the originally stored data is more difficult to write in than other data. This is due to a property of the ferroelectric material used.
This property of a ferroelectric material is called "imprinting". Thus, although a ferroelectric material has the advantage of enduring an extremely large number of times of rewriting, it also has the disadvantage of such imprinting. As a result, ferroelectric memories, which are prone to data errors after long-time use, have conventionally been regarded as rather unreliable.